Australian climate scientist Barry Pittock gave a terrific and terrifying talk at the 20th Anniversary of the Climate Insitute last week. He made the case that the U.N.’s Intergovernmental Panel on Climate Change (IPCC), the key international process for determining the “consensus” view on climate, is systematically underestimating the future impacts of climate change. Since Pittock was a major contributor to the IPCC’s Third Assessment Report (2001) and since their Fourth Assessment is due out next year, we should pay attention to what he says.

You can see all of Pittock’s 10 reasons online in the abstract for his talk. Let me pull out four of the underestimations:

1. “The climate sensitivity, or global warming after a doubling of the pre-industrial carbon dioxide concentration, is probably in the range of 2º–6°C rather than the 2001 IPCC estimate of 1.5º–4.5ºC. This suggests a more than 50% chance of that global warming by 2100 will be 3ºC or more, a level that many consider dangerous.”

3. “Permafrost melting is widespread,” which “leads to emissions of carbon dioxide and methane,” a dangerous vicious climate cycle that CP has written about.

7. & 8. “Rapid changes in Antarctica” and “Rapid melting and faster outlet glaciers in Greenland,” which combine to threaten far faster and greater sea level rise than climate models have been predicting.

I found his talk very compelling as it matched what I’ve been hearing from a number of climate scientists I interviewed for my book, including James Hansen. Pittock concludes:

The above lines of evidence (supported by well over 100 recent scientific papers), while not definitive and in some cases controversial, suggest that the balance of evidence may be swinging toward a more extreme outcome. While some of the observations may be due merely to natural fluctuations, their conjunction and, in several cases, amplifying effects are causes for concern. They suggest that critical levels of global warming may occur at even lower greenhouse gas concentrations and emissions than was considered justified in the Third Assessment Report of the Intergovernmental Panel on Climate Change report issued in 2001.

In short, the time for inaction has run out.

For those interested in Pittock’s analysis, he published a version in EOS, but you need a subscription. You can, however, get all the scientific references here. The article ends with a key point that he reiterated in his talk, which defines the nature of scientific responsibility in a world of accelerating global warming:

The above recent developments simply might mean that the science is progressing, but it also may suggest that up until now many scientists may have consciously or unconsciously downplayed the more extreme possibilities at the high end of the uncertainty range, in an attempt to appear moderate and ‘responsible’ (that is, to avoid scaring people). However, true responsibility is to provide evidence of what must be avoided: to define, quantify, and warn against possible dangerous or unacceptable outcomes.

3 Responses to Ten Reasons Why Climate Change May Be More Severe than Projected

[…] ClimateProgress has posted on this subject many times, including “Ten Reasons Why Climate Change May Be More Severe than Projected” and “The Permafrost is not so Perma.” It is always a surprise to people when I tell them that no IPCC models include the feedback from a melting permafrost, and thus all the models severely underestimate likely future impacts. […]

Climate scientists have always amazed me and continue to do so more every day. Mainly because there are so many of them and they all have different opinions. But one characteristic is common throughout them, they can predict the future. I am not sure how they do it but it is truly magical. They can take data, often very limited in scope, quality, and quantity – especially in the realm of complex climate patterns that have been changing and evolving over the past four billion years- and extrapolate it to generate the dire consequences predicted for the future. No other scientists can do this is what makes it really special. In this day and age it is definitely advantageous for your career as a scientist to perfect this skill. Although I think that climate scientists should use past lottery data to predict the winning numbers if they really need the money.

‘the hour is late, the need is pressing.’ we have little time and the children have less.Temperature affects things the individual organism has to deal with in its own life history.we have a framework to really quantify the way ecological systems respond to climate change.“That’s necessary if you want to make predictions about the effects of climate change.”